Is there a IsDefinedQ function?
99415
Implementing a safe ValueQ that does not evaluate its argument
80608
JavaScript check if variable exists (is defined/initialized)
74483
Correct way to detect sequence parameter?
20684
Test if string is a guid without throwing exceptions?
75417
Detect highest order of derivative in expression?
36989
Determining functions from specifications...
114466
How do I determine if a column is defined as a serial data type instead of an integer based off the catalog?
52179
What's a functional replacement for if-then statements?
10728
#ifdef replacement in the Swift language
16391
How to create complex conditional clauses / queries?
125393
Confirm if sub-query is selective?
30987
How to tell if a JavaScript function is defined
43481
Returning query results in predefined order
141197
In JavaScript, is there an easier way to check if a property of a property exists?
100062
Can we have a "isprotected" search operator?
48742
What does object.isQueryable() actually mean?
111147
Conditional Linq Queries