whence

Gamma: Version 4.0
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# `whence`

`whence` -- gives input information.

## Syntax

    whence (s_exp)

## Arguments

`s_exp`

  Any Gamma or Lisp expression.

## Returns

A list whose car is the input source, and whose cdr is an integer showing the sequential input order of the expression.

## Description

This function checks the input source and sequence of any given Gamma expression. It returns this information in the form of a list. The sequence number is assigned the first time the expression is used, and does not change. The `whence` call itself is a Gamma expression, and thus generates a sequence number each time it is called.

| This function requires Gamma to be running in debugging mode. To start debugging mode, you must include the `-d` option when starting Gamma.

## Example

        [~/w/devel/lisp]$ gamma -d
        Gamma(TM) Advanced Programming Language
        Copyright (C) Cogent Real-Time Systems Inc., 1996.  All rights reserved.
        Version 2.4 Build 147 at Sep 13 1999 17:15:51
        Gamma> c = 12;
        12
        Gamma> d = 14;
        14
        Gamma> whence(c);
        ("stdin" 1)
        Gamma> whence(d);
        ("stdin" 2)
        Gamma> f = 16;
        16
        Gamma> whence(f);
        ("stdin" 6)
        Gamma>

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