[#BN_sub]
= BN&lowbar;sub
:mrdocs:

Subtract signed BIGNUMs&colon; `r` &equals; `a` &hyphen; `b&period;`

== Synopsis

Declared in `&lt;openssl&sol;bn&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN&lowbar;sub(
    xref:BIGNUM.adoc[BIGNUM]* r,
    xref:BIGNUM.adoc[BIGNUM] const* a,
    xref:BIGNUM.adoc[BIGNUM] const* b);
----

== Return Value

1 on success, or 0 on error&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *r*
| Destination difference&period;
| *a*
| Minuend&period;
| *b*
| Subtrahend&period;
|===


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