make [xyz]{lin,log}vals work with dim-length of one

Basic/Core/Basic.pm

@@ -153,6 +153,7 @@ etc. see L<zeroes|PDL::Core/zeroes>.
 =for ref
 
 X axis values between endpoints (see L</xvals>).
+Works with dim-length of one as of 2.093.
 
 =for usage
 
@@ -188,6 +189,7 @@ See L</xlinvals> for more information.
 =for ref
 
 X axis values logarithmically spaced between endpoints (see L</xvals>).
+Works with dim-length of one as of 2.093.
 
 =for usage
 
@@ -241,12 +243,12 @@ sub PDL::zvals {
 sub _dimcheck {
   my ($pdl, $whichdim, $name) = @_;
   my $dim = $pdl->getdim($whichdim);
-  barf "Must have at least two elements in dimension for $name" if $dim <= 1;
+  barf "Must have at least one element in dimension for $name" if $dim < 1;
   $dim;
 }
 sub _linvals {
   my ($pdl, $v1, $v2, $dim, $method) = @_;
-  $pdl->$method * (($v2 - $v1) / ($dim-1)) + $v1;
+  $pdl->$method * (($v2 - $v1) / ($dim > 1 ? ($dim-1) : 1)) + $v1;
 }
 sub PDL::xlinvals {
   _linvals(@_[0..2], _dimcheck($_[0], 0, 'xlinvals'), 'xvals');
@@ -262,7 +264,7 @@ sub _logvals {
   my ($pdl, $min, $max, $dim, $method) = @_;
   barf "min and max must be positive" if $min <= 0 || $max <= 0;
   my ($lmin,$lmax) = map log($_), $min, $max;
-  exp($pdl->$method * (($lmax - $lmin) / ($dim-1)) + $lmin);
+  exp($pdl->$method * (($lmax - $lmin) / ($dim > 1 ? ($dim-1) : 1)) + $lmin);
 }
 sub PDL::xlogvals {
   _logvals(@_[0..2], _dimcheck($_[0], 0, 'xlogvals'), 'xvals');

Changes

@@ -1,3 +1,5 @@
+- [xyz]{lin,log}vals now works with dim-length of one
+
 2.092 2024-09-07
 - add Type::howbig
 - restore ABI (https://github.com/moocow-the-bovine/PDL-VectorValued/issues/10 https://github.com/PDLPorters/PDL-Stats/issues/33) - thanks @sebastic for report

t/basic.t

@@ -46,6 +46,10 @@ ok(tapprox($z->mv(2,0)->uniqvec->flat,pdl(0..25)/5-3),"zlinvals values"); #12
 $a1->inplace->xvals;
 my $got = $a1->slice('(10),(0),(0)');
 ok tapprox($got, 10), 'inplace xvals works' or diag "got:$got";
+eval { zeroes(1)->xlinvals(5,10) };
+is $@, '', 'can have dim-length of one *linvals';
+eval { zeroes(0)->xlinvals(5,10) };
+like $@, qr/at least one/, 'cannot have zero-length dim *linvals';
 }
 
 {
@@ -59,6 +63,10 @@ ok(all($x->shape==$zl->shape),"zlogvals shape"); #15
 ok(tapprox($xl->uniqvec->flat->log10,pdl(2..12)),"xlogvals values"); #16
 ok(tapprox($yl->mv(1,0)->uniqvec->flat->log10,pdl(-3..2)),"ylogvals values"); #17
 ok(tapprox($zl->mv(2,0)->uniqvec->flat->log10,pdl(-10..-3)),"zlogvals values");#18
+eval { zeroes(1)->xlogvals(5,10) };
+is $@, '', 'can have one-element *logvals';
+eval { zeroes(0)->xlogvals(5,10) };
+like $@, qr/at least one/, 'cannot have zero-element *logvals';
 }
 #test axisvals
 my $z = axisvals(zeroes(3,4,5,6),3);