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| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version

## if*

Arguments: (test-form {then then-form+ | thenret} {elseif else-test-form {then else-then-form+ | thenret}}* [else else-form+])

This form consists of a series of clauses introduced by the symbols `then`, `elseif`, `else`, and `thenret`. First the predicate test-form is evaluated. If it is true, the then-forms are evaluated, and the value of the last such form is returned. If test-form evaluates to `nil`, any remaining clauses are processed. If no clauses remain, if* returns `nil`.

When a `thenret` clause is encountered no further evaluation takes place, and the value of the most recently evaluated test-form is returned.

When an `elseif` clause is encountered, the predicate else-test-form is evaluated. If it is true, the else-then-forms are evaluated, and the value of the last such form is returned; otherwise any remaining clauses are processed. If no clauses remain, if* returns `nil`. And lastly, when an `else` clause is encountered, the else-forms are evaluated, and the value of the last such form is returned.

### Examples

    ;; The basic format of a IF* expression is:
    ;;
    ;; (if* [test] then [do this 1] [do this 2] else [do other 1] [do other 2])
    ;;
    ;; When [test] is true, the forms after the THEN are evaluated and the
    ;; result of the last returned; if [test] if false, the forms after the
    ;; ELSE are evaluated and the result of the last is returned.

    ;; So:

    cl-user(18): (if* (> 3 2) then "three is bigger" 3
                         else "three is smaller" 2)
    3
    ;;  Your do not need an ELSE form:
    cl-user(19): (if* (> 3 2) then "three is bigger" 3)
    3
    cl-user(19): (if* (> 2 3) then "two is bigger" 2)
    nil

    ;; You can have multiple fors after THEN or ELSE:
    cl-user(21): (defun foo (x) (if* x then (setq y 2) (print x)
                                     else (setq y -2) "no"))
    foo
    cl-user(22): (foo 2)

    2
    2
    cl-user(23): (foo "hello")

    "hello"
    "hello"
    cl-user(24): (foo nil)
    "no"
    cl-user(25):

    ;; There are two more special symbols: THENRET and ELSEIF.

    ;; THENRET says when the test is true just return the value of the test
    ;; form just evaluated:

    cl-user(25): (if* (+ 4 5) thenret)
    9
    cl-user(26):

    ;; ELSEIF introduces a new test, so you can have compound tests:

    cl-user(27): (setq score 77)
    77
    cl-user(28): (if* (< score 60) then "F"
                         elseif (< score 70) then "D"
    		     elseif (< score 80) then "C"
                         elseif (< score 90) then "B"
                         else "A")
    "C"
    cl-user(29): (setq score 55)
    55
    cl-user(30): (if* (< score 60) then "F"
                         elseif (< score 70) then "D"
    		     elseif (< score 80) then "C"
                         elseif (< score 90) then "B"
                         else "A")
    "F"
    cl-user(31): (setq score 92)
    92
    cl-user(32): (if* (< score 60) then "F"
                         elseif (< score 70) then "D"
    		     elseif (< score 80) then "C"
                         elseif (< score 90) then "B"
                         else "A")
    "A"
    cl-user(33):

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.

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| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version