Maxima Manual

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2.2 Lisp and Maxima

All of Maxima is of course written in lisp. There is a naming convention for functions and variables: All symbols which begin with a "$" sign at lisp level, are read with the "$" sign stripped off at Macsyma level. For example, there are two lisp functions TRANSLATE and $TRANSLATE. If at macsyma level you enter TRANSLATE(FOO); the function which is called is the $translate function. To access the other function you must prefix with a "?". Note you may not put a space after the ? since that would indicate you were looking for help!

(C1) ?TRANSLATE(FOO);

Of course, this may well not do what you wanted it to do since it is a completely different function.

To enter a lisp command you may use

(C1) :lisp (foo 1 2)
or to get a lisp prompt use to_lisp();, or alternately type Ctrl-c to enter into a debug break. This will cause a lisp break loop to be entered. You could now evaluate $d2 and view the value of the line label D2, in its internal lisp format. Typing :q will quit to top level, if you are in a debug break. If you had exited maxima with to_lisp(); then you should type

MAXIMA>(run)
at the lisp prompt, to restart the Maxima session.

If you intend to write lisp functions to be called at macsyma level you should name them by names beginning with a "$". Note that all symbols typed at lisp level are automatically read in upper case, unless you do something like |$odeSolve| to force the case to be respected. Maxima interprets symbols as mixed case, if the symbol has already been read before or at the time it was first read there was not an already existing symbol with the same letters but upper case only. Thus if you type

(C1) Integrate; (D1) INTEGRATE (C2) Integ; (D2) Integ
The symbol Integrate already existed in upper case since it is a Maxima primitive, but INTEG, does not already exist, so the Integ is permitted. This may seem a little bizarre, but we wish to keep old maxima code working, which assumes that Maxima primitives may be in upper or lower case. An advantage of this system is that if you type in lower case, you will immediately see which are the maxima keywords and functions.

To enter Maxima forms at lisp level, you may use the #$ macro.

(setq $foo #$[x,y]$)

This will have the same effect as entering

(C1)FOO:[X,Y];

except that foo will not appear in the VALUES list. In order to view foo in macsyma printed format you may type

(displa $foo)

In this documentation when we wish to refer to a macsyma symbol we shall generally omit the $ just as you would when typing at macsyma level. This will cause confusion when we also wish to refer to a lisp symbol. In this case we shall usually try to use lower case for the lisp symbol and upper case for the macsyma symbol. For example LIST for $list and list for the lisp symbol whose printname is "list".

Since functions defined using the MAXIMA language are not ordinary lisp functions, you must use mfuncall to call them. For example:

(D2) FOO(X, Y) := X + Y + 3

then at lisp level

CL-MAXIMA>>(mfuncall '$foo 4 5) 12

A number of lisp functions are shadowed in the maxima package. This is because their use within maxima is not compatible with the definition as a system function. For example typep behaves differently common lisp than it did in Maclisp. If you want to refer to the zeta lisp typep while in the maxima package you should use global:typep (or cl:typep for common lisp). Thus

(macsyma:typep '(1 2)) ==> 'list (lisp:typep '(1 2))==> error (lisp:type-of '(1 2))==> 'cons

To see which symbols are shadowed look in "src/maxima-package.lisp" or do a describe of the package at lisp level.