📄 bc.1
字号:
4785(the)S4936(variable)S7248 V1080("a".)S1285(What)S1531(this)S1704(does)S1916(in)S10 B2022(bc)S10 R2151(is)S2245(assign)S2523(the)S2673(value)S2918(3)S2995(to)S3100(the)S3250(variable)S3602("a")S3756(and)S3928(then)S4128(compare)S4502(3)S4579(to)S4684(5.)S4811(It)S4900(is)S4994(best)S5183(to)S7368 V1080(use)S1239(parenthesis)S1717(when)S1960(using)S2202(relational)S2608(and)S2778(logical)S3077(operators)S3477(with)S3681(the)S3829(assignment)S4306(operators.)S7903 V720(Page)S941(3)S2936(\()S2978(.)S3011(\))S4455(September)S4911(13,)S(1996)200 5061 A8143 VEP%%Page: 4 4BP/slant 0 def/height 0 def480 V10 R720(bc)S823(\()S865(1)S923(\))S2696(Eighth)S(Edition)296 2989 A5024(bc)S5127(\()S5169(1)S5227(\))S960 V1080(There)S1346(are)S1500(a)S1575(few)S1758(more)S1996(special)S2307(expressions)S2807(that)S2989(are)S3144(provided)S3532(in)S10 B3641(bc)S10 R3742(.)S3823(These)S4095(have)S4316(to)S4425(do)S4556(with)S4766(user)S4965(de\256ned)S1080 V1080(functions)S1480(and)S1651(standard)S2018(functions.)S2468(They)S2701(all)S2828(appear)S3123(as)S3232(")S10 I3273(name)S10 B3491(\()S10 I3525(parameters)S10 B3983(\))S10 R4017(".)S4133(See)S4304(the)S4452(section)S4762(on)S4887(functions)S1200 V1080(for)S1223(user)S1416(de\256ned)S1737(functions.)S2186(The)S2368(standard)S2734(functions)S3133(are:)S1368 V1080(length)S1356(\()S1415(expression)S1870(\))S1488 V1440(The)S1622(value)S1865(of)S1974(the)S2122(length)S2398(function)S2758(is)S2850(the)S2998(number)S3330(of)S3439(signi\256cant)S3883(digits)S4131(in)S4234(the)S4382(expression.)S1656 V1080(read)S1279(\()S1338(\))S1440(The)S1635(read)S1847(function)S2220(\(an)S2387(extension\))S(will)157 2844 A3039(read)S3252(a)S3336(number)S3682(from)S3917(the)S4079(standard)S(input,)231 4459 A4729(regardless)S5177(of)S1776 V1440(where)S1715(the)S1866(function)S2229(occurs.)S2595(Beware,)S2957(this)S3129(can)S3296(cause)S3547(problems)S3948(with)S4154(the)S4304(mixing)S4615(of)S4726(data)S4921(and)S5093(pro-)S1896 V1440(gram)S1679(in)S1789(the)S1944(standard)S(input.)231 2317 A2606(The)S2796(best)S2991(use)S3158(for)S3309(this)S3487(function)S3855(is)S3955(in)S4066(a)S4144(previously)S(written)286 4601 A4920(program)S2016 V1440(that)S1621(needs)S(input)206 1880 A2116(from)S2342(the)S2495(user,)S2718(but)S2876(never)S3130(allows)S3423(program)S3794(code)S4014(to)S4121(be)S(input)206 4245 A4480(from)S4705(the)S4857(user.)S5104(The)S2136 V1440(value)S1689(of)S1804(the)S1958(read)S2163(function)S2529(is)S2627(the)S2782(number)S3121(read)S3327(from)S3555(the)S3710(standard)S(input)206 4083 A4321(using)S4570(the)S4725(current)S5043(value)S2256 V1440(of)S1549(the)S1697(variable)S10 B2047(ibase)S10 R2290(for)S2433(the)S(conversion)441 2581 A3047(base.)S2424 V1080(scale)S1307(\()S1366(expression)S1821(\))S2544 V1440(The)S1630(value)S1881(of)S1998(the)S2154(scale)S2389(function)S2757(is)S2857(the)S3013(number)S3353(of)S3470(digits)S3726(after)S3945(the)S4102(decimal)S4455(point)S4695(in)S4807(the)S4964(expres-)S2664 V1440(sion.)S2832 V1080(sqrt)S1256(\()S1315(expression)S1770(\))S2952 V1440(The)S1628(value)S1877(of)S1992(the)S2146(sqrt)S2328(function)S2695(is)S2794(the)S2949(square)S3244(root)S3438(of)S3554(the)S3709(expression.)S4221(If)S4321(the)S4476(expression)S4938(is)S5037(nega-)S3072 V1440(tive,)S1641(a)S1711(run)S1870(time)S2074(error)S2296(is)S2388(generated.)S3240 V870(S)S872(ST)S930(TA)S994(AT)S1069(TE)S1133(EM)S1197(ME)S1288(EN)S1352(NT)S1427(TS)S1491(S)S3360 V1080(Statements)S1559(\(as)S1714(in)S1830(most)S2063(algebraic)S(languages\))436 2471 A2945(provide)S3290(the)S3451(sequencing)S3941(of)S4063(expression)S4531(evaluation.)S5038(In)S10 B5160(bc)S3480 V10 R1080(statements)S1536(are)S1691(executed)S2079("as)S(soon)189 2234 A2453(as)S2567(possible.")S3017(Execution)S3455(happens)S3814(when)S4062(a)S4137(newline)S4486(in)S(encountered)492 4594 A5116(and)S3600 V1080(there)S1313(is)S1411(one)S1587(or)S1702(more)S1940(complete)S2340(statements.)S2846(Due)S3045(to)S3154(this)S3330(immediate)S3786(execution,)S4233(newlines)S4622(are)S4777(very)S4987(impor-)S3720 V1080(tant)S1268(in)S10 B1382(bc)S10 R1483(.)S1544(In)S1664(fact,)S1877(both)S2091(a)S2172(semicolon)S2621(and)S2802(a)S2883(newline)S3238(are)S3398(used)S3618(as)S3738(statement)S4160(separators.)S4655(An)S4814(improperly)S3840 V(placed)263 1080 A1376(newline)S(will)157 1728 A1918(cause)S2175(a)S2253(syntax)S2548(error.)S(Because)336 2828 A3197(newlines)S3588(are)S3745(statement)S4164(separators,)S4631(it)S4720(is)S4820(possible)S5183(to)S3960 V1080(hide)S1293(a)S1378(newline)S1737(by)S1877(using)S2134(the)S2297(backslash)S2727(character.)S3187(The)S3383(sequence)S3791("\\<nl>",)S4157(where)S4443(<nl>)S4674(is)S4780(the)S4942(newline)S4080 V1080(appears)S1413(to)S10 B1516(bc)S10 R1642(as)S(whitespace)448 1752 A2226(instead)S2537(of)S2647(a)S2718(newline.)S3113(A)S3212(statement)S3624(list)S3773(is)S3866(a)S3937(series)S4193(of)S4303(statements)S4754(separated)S5161(by)S4200 V1080(semicolons)S1562(and)S1737(newlines.)S2175(The)S2362(following)S2783(is)S2880(a)S2955(list)S3108(of)S10 B3222(bc)S10 R3353(statements)S3808(and)S3983(what)S4208(they)S4410(do:)S4567(\(Things)S4909(enclosed)S4320 V1080(in)S1183(brackets)S(\([]\))136 1544 A1705(are)S1854(optional)S2208(parts)S2429(of)S2538(the)S2686(statement.\))S4488 V1080(expression)S4608 V1440(This)S1645(statement)S2057(does)S2267(one)S2438(of)S2548(two)S2725(things.)S3046(If)S3140(the)S3289(expression)S3745(starts)S3984(with)S4189("<variable>)S4695(<assignment>)S4728 V(...",)141 1440 A1622(it)S1719(is)S1826(considered)S2302(to)S2420(be)S2555(an)S2690(assignment)S3182(statement.)S3658(If)S3766(the)S3929(expression)S4399(is)S4506(not)S4674(an)S4809(assignment)S4848 V1440(statement,)S1877(the)S2026(expression)S2482(is)S2575(evaluated)S2988(and)S3160(printed)S3472(to)S3577(the)S3727(output.)S4060(After)S4301(the)S4451(number)S4785(is)S4879(printed,)S5216(a)S4968 V1440(newline)S1792(is)S1892(printed.)S2260(For)S2433(example,)S2832("a=1")S3099(is)S3198(an)S3325(assignment)S3809(statement)S4227(and)S4404("\(a=1\)")S4738(is)S4837(an)S4964(expres-)S5088 V1440(sion)S1642(that)S1828(has)S1997(an)S2127(embedded)S2575(assignment.)S3113(All)S3278(numbers)S3660(that)S3847(are)S4007(printed)S4328(are)S4488(printed)S4809(in)S4923(the)S5082(base)S5208 V1440(speci\256ed)S1833(by)S1968(the)S2125(variable)S10 B2484(obase)S10 R2724(.)S2783(The)S2974(legal)S3204(values)S3495(for)S10 B3647(obase)S10 R3921(are)S4079(2)S(through)312 4163 A4509(BC_BASE_MAX.)S5328 V1440(\(See)S1656(the)S1815(section)S2136(LIMITS.\))S2593(For)S2769(bases)S3023(2)S(through)312 3109 A3457(16,)S3618(the)S3777(usual)S(method)301 4025 A4362(of)S(writing)291 4483 A4811(numbers)S5194(is)S5448 V1440(used.)S1725(For)S1916(bases)S2185(greater)S2517(than)S2740(16,)S10 B2915(bc)S10 R3066(uses)S3289(a)S(multi-character)617 3384 A4051(digit)S(method)301 4285 A4636(of)S4770(printing)S5138(the)S5568 V1440(numbers)S1824(where)S(each)185 2109 A2332(higher)S2627(base)S2844(digit)S3066(is)S3171(printed)S3494(as)S3616(a)S3699(base)S3916(10)S4054(number.)S4449(The)S(multi-character)617 4644 A5688 V1440(digits)S1711(are)S1883(separated)S2312(by)S(spaces.)288 2460 A2821(Each)S3071(digit)S3303(contains)S3686(the)S3857(number)S4212(of)S4343(characters)S4800(required)S5183(to)S5808 V1440(represent)S1852(the)S2017(base)S2238(ten)S2403(value)S2663(of)S2789("obase-1".)S3276(Since)S3542(numbers)S3930(are)S4096(of)S4222(arbitrary)S4612(precision,)S5049(some)S5928 V1440(numbers)S1814(may)S2015(not)S2171(be)S2294(printable)S2680(on)S2807(a)S2879(single)S3146(output)S3429(line.)S3657(These)S(long)178 3925 A4130(numbers)S(will)157 4503 A4687(be)S(split)173 4809 A5009(across)S6048 V1440(lines)S1659(using)S1905(the)S2057("\\")S2196(as)S2309(the)S2461(last)S2630(character)S3030(on)S3159(a)S3233(line.)S3463(The)S3649(maximum)S4085(number)S4422(of)S4536(characters)S4976(printed)S6168 V1440(per)S1603(line)S1788(is)S1889(70.)S2073(Due)S2274(to)S2385(the)S2541(interactive)S3000(nature)S3285(of)S10 B3402(bc)S10 R3536(printing)S3887(a)S3965(number)S4305(cause)S4562(the)S4718(side)S4913(effect)S5177(of)S6288 V1440(assigning)S1844(the)S1992(printed)S2302(value)S2545(the)S2694(the)S2843(special)S3149(variable)S10 B3500(last)S10 R3651(.)S3702(This)S3907(allows)S4196(the)S4345(user)S4539(to)S4643(recover)S4972(the)S5121(last)S6408 V1440(value)S1693(printed)S(without)307 2013 A2355(having)S2663(to)S2776(retype)S3063(the)S3221(expression)S3686(that)S3872(printed)S4192(the)S4350(number.)S4742(Assigning)S5183(to)S6528 V10 B1440(last)S10 R1633(is)S1742(legal)S1980(and)S(will)157 2167 A2366(overwrite)S2795(the)S2960(last)S3142(printed)S3469(value)S3729(with)S3950(the)S4115(assigned)S4504(value.)S4815(The)S5015(newly)S6648 V1440(assigned)S1811(value)S(will)157 2054 A2236(remain)S(until)184 2541 A2750(the)S2898(next)S3096(number)S3428(is)S3520(printed)S3830(or)S3939(another)S4266(value)S4509(is)S4601(assigned)S4972(to)S10 B5075(last)S10 R5226(.)S6816 V1080(string)S1440(The)S1627(string)S1886(is)S1983(printed)S2298(to)S2406(the)S2559(output.)S2895(Strings)S3210(start)S3414(with)S3623(a)S(double)273 3698 A(quote)223 4001 A4255(character)S4657(and)S4833(contain)S5160(all)S6936 V1440(characters)S(until)184 1889 A2112(the)S2274(next)S(double)273 2486 A(quote)223 2798 A3060(character.)S3520(All)S3688(characters)S4137(are)S4299(take)S(literally,)339 4505 A4882(including)S7056 V1440(any)S1610(newline.)S2004(No)S2152(newline)S2496(character)S2892(is)S2984(printed)S3294(after)S3505(the)S3653(string.)S7224 V10 B1080(print)S10 R1324(list)S7344 V1440(The)S1631(print)S1855(statement)S2275(\(an)S2438(extension\))S2891(provides)S3272(another)S(method)301 3609 A3945(of)S4064(output.)S4405(The)S4597("list")S4837(is)S4939(a)S5019(list)S5177(of)S7464 V1440(strings)S1734(and)S1905(expressions)S2400(separated)S2807(by)S2933(commas.)S3344(Each)S3572(string)S3827(or)S3937(expression)S4393(is)S4486(printed)S4797(in)S4900(the)S5048(order)S7903 V720(September)S1176(13,)S(1996)200 1326 A2936(\()S2978(.)S3011(\))S4990(Page)S5211(4)S8143 VEP%%Page: 5 5BP/slant 0 def/height 0 def480 V10 R720(bc)S823(\()S865(1)S923(\))S2696(Eighth)S(Edition)296 2989 A5024(bc)S5127(\()S5169(1)S5227(\))S960 V1440(of)S1561(the)S1721(list.)S1931(No)S2091(terminating)S2592(newline)S2948(is)S3052(printed.)S3424(Expressions)S3947(are)S4108(evaluated)S4532(and)S4715(their)S4938(value)S5194(is)S1080 V1440(printed)S1754(and)S1928(assigned)S2303(the)S2455(the)S2607(variable)S10 B2961(last)S10 R3112(.)S3166(Strings)S3480(in)S3587(the)S3739(print)S3958(statement)S4373(are)S4526(printed)S4840(to)S4947(the)S5099(out-)S1200 V1440(put)S1600(and)S1777(may)S1983(contain)S2312(special)S2625(characters.)S3118(Special)S3448(characters)S3891(start)S4098(with)S4310(the)S4466(backslash)S4890(character)S1320 V1440(\(\\\).)S1616(The)S1803(special)S2113(characters)S(recognized)442 2553 A3025(by)S10 B3155(bc)S10 R3286(are)S3440("b")S3602(\(bell\),)S3876("f")S4022(\(form)S4281(feed\),)S4543("n")S4704(\(newline\),)S5145("r")S1440 V1440(\(carriage)S1834(return\),)S2168("t")S2312(\(tab\),)S2562(and)S2741("\\")S2886(\(backslash\).)S3430(Any)S3638(other)S3880(character)S4286(following)S4712(the)S4870(backslash)S1560 V(will)157 1440 A1622(be)S(ignored.)332 1742 A2124(This)S(still)151 2328 A2504(does)S2713(not)S2866(allow)S3115(the)S(double)273 3263 A(quote)223 3561 A3809(character)S4205(to)S4308(be)S4428(part)S4610(of)S4719(any)S4889(string.)S1728 V1080({)S1153(statement_list)S1737(})S1848 V1440(This)S1646(is)S1740(the)S(compound)423 1890 A2340(statement.)S2803(It)S2892(allows)S(multiple)335 3182 A3544(statements)S3997(to)S4103(be)S(grouped)329 4226 A4583(together)S4941(for)S5087(exe-)S1968 V1440(cution.)S2136 V10 B1080(if)S10 R1167(\()S1226(expression)S1681(\))S10 B1740(then)S10 R1956(statement1)S2417([)S10 B2451(else)S10 R2633(statement2])S2256 V1440(The)S1623(if)S1711(statement)S2124(evaluates)S2526(the)S2676(expression)S3133(and)S3305(executes)S3679(statement1)S4142(or)S4253(statement2)S4716(depending)S5161(on)S2376 V1440(the)S1601(value)S1857(of)S1979(the)S2140(expression.)S2658(If)S2764(the)S2924(expression)S3391(is)S(non-zero,)383 3495 A⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -