>>21
LET wasn't immediately invented, and if you read sufficiently old lisp code
(let ((b 2) (c 3))
(sqrt (+ (expt b 2) (expt c 2))))would be written as
((LAMBDA (B C)
(SQRT (+ (EXPT B 2) (EXPT C 2))))
2 3)they called it "lambda-binding"
lisp news for may 25, 1978 says that several standard macros have been added, LET is one of them. and explicitly defines LET as
(LET ((V1 E1) (V2 E2) . . . (VN EN)) F1 F2 . . . FK)
==>
((LAMBDA (V1 V2 . . . VN)
F1 F2 . . . FK)
E1 E2 . . . EN)and then sept 17, 1978,
[1] New autoloadable interpreter macros: backquote ("`") and LET.
The "backquote" macro and the LET macro will be autoloaded when used.
...
The LET macro provides a convenient way to lambda-bind variables to
values. Its usages is as follows:
(LET ((var1 val1) (var2 val2) . . . (varn valn))
<form1>
. . .
<formn>)
One may substitute merely "var" in place of "(var NIL)"
For example:
(LET ((A 1) (B 2) C)
<forms>)
Binds A to 1, B to 2, and C to NIL and then evaluates <forms>.