ときどきの雑記帖 RE* (新南口)

Tears in Rain

バビロンプロジェクト

読む前に想像してたのと違った(笑)

jai

jaiってなんだろうと思ったら、(現時点では)オープンになっていない プログラミング言語処理系だそうな。

I’m also frustrated at a language in closed beta being perpetually compared to a language that is open source and in production.

Your links back up the statement. The first says the compiler is proprietary and unavailable outside of some beta testers, but may be open in the great and nebulous future.

メモ

The Evolution of Ruby Strings from 1.8 to 3.2 | by Tech - RubyCademy | RubyCademy | Medium

北斗の拳＠tvk

OP変わった。

The Origins of Python

興味深く読んだ。

The programming language used at the London workshop in 1970 was TELCOMP,3 a simple unstructured language similar to BASIC—not BASIC as it is now, but unstructured BASIC as it was then.4 The programming language taught at the Istanbul workshop in 2019 was Python,5 a programming language designed by Guido van Rossum that has become wildly popular,6 steadily gaining in popularity since an inconspicuous public release in 1991. As far apart as these events are, both in time and geography, an arc of history connects them.

このTELCOMPというのはたぶん初めて見た名前だと思うけど

1.01 DO PART 2 FOR I = 1:1:N-1

2.01 DO PART 3 FOR J = 1:1:N-1

3.01 DO PART 4 IF A[J] > A[J+1]

4.01 SET X = A[J]
4.02 SET A[J] = A[J+1]
4.03 SET A[J+1] = X

こんな感じのコードなのだとか。 行頭に番号がつくのはBASICっぽいけど.がついているのがポイント(BASICと違う点)で、 .の前の部分が処理の塊(ブロック)を表し、 あとの部分がブロックの中でのシーケンスを表していると。

https://walden-family.com/bbn/bbn-print2.pdf p.81

4.2 Higher-level language work LGP-30 compiler extensions

こんなところにもLGP-30が。

JOSS

このTELCOMP、JOSSの流れを汲むものであったということなので JOSSも見てみるとなるほど共通点が多い(つーか こっちの名前は聞き覚えがあったけどどんなソースコードになるのかは知らなかった)。

Loops and conditions

JOSS uses a suffix notation to indicate conditional evaluation, “do this if this is true”, in contrast to most languages which place the condition in front in prefix notation, “if this is true, do this”. Like BASIC, but unlike FORTRAN or FOCAL, any statement can be conditionally evaluated in this fashion. For example, to print a string only if a condition is met, one can combine the if with a Type:

1.1 Type "Hello, World!" if X=5.

Perlの後置if(if修飾子)ってこれから来たんだろうか?

このほかにも面白い(特徴的な)仕様があって、たとえば

Expressions and propositions

A unique feature of JOSS was its handling of logical expressions. Most computer languages offer some way to form a multi-part mathematical expression, for instance, Set x=(1+2)·3. which sets the variable x to the value 9. JOSS expanded on this concept by clearly defining the concept of the “proposition”, an expression that returns a logical value, true or false, instead of a numeric one. They were mostly seen in If statements, as in the examples above, but the boolean value could also be stored in a variable directly,[33] or one could convert true to 1 and false to 0 using the tv (truth value) function.[34]

In addition to propositions, JOSS also had the concept of “conditional expressions”. These consisted of strings of propositions along with code that would run if that proposition was true. This allowed multi-step decision trees to be written in a single line. They serve a purpose similar to the ternary operator found in modern languages like C or Java, where they are used to return a value from a compact structure implementing if-then-else. JOSS’ version has any number of conditionals, not just three, so it is more of a compact switch statement than a compact if-then.[35]

This example recreates the function of the sgn function:[36]

Let s(x)=[x=0:0; x>0:1; x<0:-1].

JOSSにもletがあったようで、時期的にはBASICより早くて最初期の部類?

Let

Let was used to define user-defined functions.[39] Equivalent to BASIC’s DEF FN.[30]

Let t(x)=sin(x)/cos(x).
Set j=t(1.1).
Type j.

Let can also be used to set the value of a variable using a formula consisting of a constant:

Let x=5.
Sample program 
1.1 Demand p,q.
1.2 Stop if q<0 or r(q,2)=0.
1.3 Set a=1.
1.4 Do part 2 while q>1 and a≠0.
1.5 Type a in form 3.
1.6 Stop.

2.1  Do part 20.
2.1  Do part 11 if p<0.
2.2  Do part 12 if p≥q.
2.3  Do part 13 if p=0.
2.4  Done if a=0.
2.5  Set p=p/4 while r(p,4)=0.
2.6  Do part 14 if r(p,2)=0.
2.7  Do part 20.
2.8  Set a=-a if r(p,4)=r(q,4)=3.
2.9  Set s=p, p=q, q=s.
2.95 Do part 20.

11.1 Set a=-a if r(q,4)=3.
11.2 Set p=|p|.
11.3 Do part 20.

12.1 Set p=r(p,q).
12.2 Do part 20.

13.1 Set a=0, p=1, q=1.

14.1 Set a=-a if r(q,8)=3 or r(q,8)=5.
14.2 Set p=p/2.

20.1 Type p, q in form 1 if a=1.
20.2 Type p, q in form 2 if a=-1.

Form 1: "  L(%.0f,%.0f)  ="
Form 2: "  -L(%.0f,%.0f)  ="
Form 3: "  %.0f\n"

翻訳

翻訳記事が出ていた＞The Origins of Python

ブログ: Pythonの起源

GNU C Language Intro and Reference

以前ちょっと触れた GNU C Language Intro and Reference の最終結果に出てこない部分について。

見出し(セクション名)でいうと以下の三つ。

  • @section IEEE 754 Decimal Arithmetic
  • @section Double-Rounding Problems
  • @section More on Decimal Floating-Point Arithmetic

一番目と三番目が十進浮動小数点数 (Decimal floating point - Wikipedia) の話で、二番目はIntelのx87環境で起きる(起きていた) 80ビットから64ビットへの丸目の問題の話。

十進浮動小数点数をサポートしているCPUってPOWERくらいしか知らないのだけど、 他にもあるんだろうか?

FORTRAN Compiler on IBM 704

ソースコードの構文解析では大雑把に ソースを1行読み込む(コメント行の読み飛ばし) → 算術式(ARITHMETIC)かどうかの判定 →(算術式の場合) 式の解析 →(算術式以外の場合) 文(DO、IFなど)の解析

となっているのだけど、 実は(?) ソース読み込みと算術式かどうかの判定の間に SCANS FOR HOLLERITH AND ILLEGAL CHARACTERS というステップがある。

サブルーチンとしてはこんな感じ。

       REM CD000/ CALLS=C0190X,C0190,DIAG.                              4F11681 
       REM CD000 SCANS FOR HOLLERITH AND ILLEGAL CHARACTERS.            4F11682 
CD000  TSX C0190X,4                * SET SCAN TO PICK UP 1ST CHARACTER. 4F11683 
CD001  TSX CD900,1                 * IF NOT ENDMARK OR ILLEGAL CHARACTER4F11684 
       CAS COMMA                     SCAN                               4F11685 
       TXI CD002,0                   FOR                                4F11686 
       TXI CD003,0                   HOLLERITH                          4F11687 
CD002  SUB OPEN                      SPECIFICATION                      4F11688 
       TNZ CD001                     WHICH                              4F11689 
CD003  TSX CD900,1                 * CAN BE=                            4F11690 
       SUB L(10)                     , N H                              4F11691 
       TPL CD001                     OR = ( N H.                        4F11692 
CD004  TSX CD900,1                 * IF NOT ENDMARK OR ILLEGAL CHARACTER4F11693 
       CAS L(9)                      CONTINUE SCAN.                     4F11694 
       TXI CD005,0                   N                                  4F11695 
       TXI CD004,0                   IS                                 4F11696 
       TXI CD004,0                   A                                  4F11697 
CD005  CAS L(H)                      FIXED                              4F11698 
       TXI CD001+1,0                 POINT                              4F11699 
       TXI CD700,0                   INTEGER.                           4F11700 
       TXI CD001+1,0                 X                                  4F11701 
CD700  TSX C0190,4                 * GO GET NEXT NONBLANK CHARACTER,    4F11702 
       CAS ENDMK                     AND IF ENDMARK,                    4F11703 
       TXI CD701,0                   THEN SKIP                          4F11704 
       TXI CC000,0                 * TO NON-ARITHMETIC CLASSIFICATION.  4F11705 
CD701  TSX CD600,1                 * SINCE HOLLERITH HAS BEEN FOUND,    4F11706 
       TXI CD700,0                   THEN $ IS LEGAL IN FORMAT TEST.    4F11707 
CD900  TSX C0190,4                 * OBTAIN NEXT NONBLANK CHARACTER,    4F11708 
       CAS ENDMK                     AND IF NOT                         4F11709 
       TXI CD800,0                   ENDMARK, THEN SKIP                 4F11710 
       TXI CB000,0                 * EXIT TO ARITH/NON-ARITH SCAN.      4F11711 
CD800  CAS SPECOP                    CHECK FOR $                        4F11712 
       TXI CD601,0                   WHICH, UNLESS HOLERITH, IS AN      4F11713 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11714 
CD600  CAS PM                        CHECK FOR RECORD MARK              4F11715 
       TRA 1,1                       WHICH IS AN                        4F11716 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11717 
CD601  CAS CHAR3                     CHECK FOR MINUS ZERO               4F11718 
       TRA 1,1                       WHICH IS AN                        4F11719 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11720 
       CAS CHAR2                     CHECK FOR PLUS ZERO                4F11721 
       TRA 1,1                       WHICH IS AN                        4F11722 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11723 
       CAS MINUS                     CHECK FOR MINUS SIGN               4F11724 
       TRA 1,1                       WHICH IS AN                        4F11725 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11726 
       SUB TEN                       CHECK FOR TEN                      4F11727 
       TNZ 1,1                       WHICH IS AN                        4F11728 
       TSX DIAG,4                  * ERROR -- GO TO DIAGNOSTIC.         4F11729 
       REM  END OF PROGRAM CD000.                                       4F11730

流れとしてはだいたい把握できている(と思っている)のだけど、 数字のならび→H→ENDMK という並びだったときに TO NON-ARITHMETIC CLASSIFICATION となるのがなぜなのかよくわからん (通常はEXIT TO ARITH/NON-ARITH SCAN)。

≪ prev Blade Runner Blues
next ≫ 眼下の敵