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.\" ========================================================================
.\"
.IX Title "Imager::Expr::Assem 3"
.TH Imager::Expr::Assem 3 "2020-06-13" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
.Vb 2
\&  Imager::Expr::Assem \- an assembler for producing code for the Imager
\&  register machine
.Ve
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&  use Imager::Expr::Assem;
\&  my $expr = Imager::Expr\->new(assem=>\*(Aq...\*(Aq, ...)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module is a simple Imager::Expr compiler that compiles a
low-level language that has a nearly 1\-to\-1 relationship to the
internal representation used for compiled register machine code.
.SS "Syntax"
.IX Subsection "Syntax"
Each line can contain multiple statements separated by semi-colons.
.PP
Anything after '#' in a line is ignored.
.PP
Types of statements:
.IP "variable definition" 4
.IX Item "variable definition"
.RS 4
.RS 4
\&\f(CW\*(C`var\*(C'\fR \fIname\fR:\fItype\fR
.RE
.RE
.RS 4
.Sp
defines variable \fIname\fR to have \fItype\fR, which can be any of \f(CW\*(C`n\*(C'\fR or
\&\f(CW\*(C`num\*(C'\fR for a numeric type or \f(CW\*(C`pixel\*(C'\fR, \f(CW\*(C`p\*(C'\fR or \f(CW\*(C`c\*(C'\fR for a pixel or
color type.
.Sp
Variable names cannot include white-space.
.RE
.IP "operators" 4
.IX Item "operators"
Operators can be split into 3 basic types, those that have a result
value, those that don't and the null operator, eg. jump has no value.
.Sp
The format for operators that return a value is typically:
.RS 4
.Sp
.RS 4
\&\fIresult\fR = \fIoperator\fR \fIoperand\fR ...
.RE
.RE
.RS 4
.Sp
and for those that don't return a value:
.Sp
.RS 4
\&\fIoperator\fR \fIoperand\fR
.RE
.RE
.RS 4
.Sp
where operator is any valid register machine operator, result is any
variable defined with \f(CW\*(C`var\*(C'\fR, and operands are variables, constants or
literals, or for jump operators, labels.
.Sp
The set operator can be simplified to:
.Sp
.RS 4
\&\fIresult\fR = \fIoperator\fR
.RE
.RE
.RS 4
.Sp
All operators maybe preceded by a label, which is any non-white-space
text immediately followed by a colon (':').
.RE
.SH "BUGS"
.IX Header "BUGS"
Note that the current optimizer may produce incorrect optimization for
your code, fortunately the optimizer will disable itself if you
include any jump operator in your code.  A single jump to anywhere
after your final \f(CW\*(C`ret\*(C'\fR operator can be used to disable the optimizer
without slowing down your code.
.PP
There's currently no high-level code generation that can generate code
with loops or real conditions.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBImager\fR\|(3), \fItransform.perl\fR, \fIregmach.c\fR
.SH "AUTHOR"
.IX Header "AUTHOR"
Tony Cook <tony@develop\-help.com>